Process and apparatus for retorting oil shale



C. E. ADAMS 'Sept. 25, 1956 PROCESS AND APPARATUS FOR RETORTING OILSHALE Filed Aug. l,- 1952 Y 2 Sheets-Sheet 1 Sept. 25, 1956 c. E; ADAMS2,764,531

PROCESS AND APPARATUS FOR RETORTING OIL SHALE Filed Aug. 1, 1952 2Sheets-Sheet 2 Q1 dr'h Adams Srzvenbor PROCESS AND APPARATUS FORREPORTING OIL SHALE Clark E. Adams, Baton Rouge, La., assignor to EssoResearch and Engineering Company, a corporation of Delaware ApplicationAugust 1, 1952, Serial No. 302,081.

1 Claim. (Cl. 20214) The present invention relates to improvements in aprocess and apparatus for retorting oil shale and the like. Theinvention is applicable also to the treatment of analogous finelydivided solid materials such as coal as well as to shale and other oilbearing solids.

In the prior art numerous processes have been proposed for retorting oilshale to recover hydrocarbon oils and other volatile or volatilizableorganic materials from rocks. In general, oil shale is processed bycrushing it to a predetermined size, heating the crushed shale to atemperature and for a sufficient time under conditions suitable fordriving off all oils and other organic matter. In this process some ofthe organic matter is carbonized leaving deposits of coke and othermaterials which cannot be volatilized and these materials are usuallyburned, the heat of combustion thereof supplying most or all of theheating for the retorting process.

It has also been proposed in the prior art to fluidize the finelydivided shale which is being treated in order to obtain more eflicientextraction or volatilization of the oil and other vaporizable organicconstituents. The present invention relates to certain improvements inthe general process just described and relates also to specific meansfor carrying out such process.

According to one aspect of the present invention raw shale which issuitably ground or crushed to a particle size which can conveniently befluidized or suspended in a dense turbulent bed by means of a gas streamis subjected to heating under retorting conditions in the presence of amass of relatively much larger, denser, non-adsorbent and relativelysmooth and inert solid particles. These particles should have an averagediameter of at least 70 microns, preferably more. The shale which israther finely divided is introduced into a fluidized bed of inertabrasion resistant and non-adsorbent solid particles such as sea sand,small pebbles, or metal shot, preferably of steel or other highlyresistant metal, with the result that the turbulent action of thecomposite fluidized bed rapidly pulverizes and disintegrates the shaleas it is being retorted. The recovery of organic matter from the shaleis enhanced due to both the disintegration of the shale particles andthe non-adsorbent and inert nature of the bulk of the bed. The crackingactivity and oil adsorptivity of the shale residue result in reduced oilyields when spent or burnt shale makes up the bulk of the retorting bed.In this invention the shale residue forms only a small proportion, lessthan 25%, of the bed as it is readily removed in a continuous mannerfrom the larger and denser particles in the retorting bed.

According to another aspect of the invention pulverization of the shalewhich is being retorted is enhanced and accelerated by first subjectingthe raw shale to relatively high pressure with gasiform fluids such ashydrocarbon gases, steam, etc. and then suddenly releasing the preheatedand pressured shale into a zone of relatively lower pressure or a zonewhere it is quickly heated, or both. The temperature in the zone ofpressure release States Patent ice may be considerably higher than thatof the preheated shale. In any case the conditions preferably are soadjusted that there is a very sudden reduction in ambient pressureand/or a relatively sudden and substantial rise in temperature with aconsequent sudden release of the occluded and dissolved gases orgasiform fluids in the preheated shale. The shale is rapidlydisintegrated and its oil or other vaporizable constituents are quicklyreleased by the procedure just described. Gaseous hydrocarbons or steammay be used as the saturating material for the preheated shale.Alternatively, any liquid may be used to saturate the shale which willvaporize at the lower pressure and/ or higher tempertaure, such asWater, extraneous hydrocarbons, or some of the product from theretorting step. The latter may be formed in situ by heating the shaleunder pressure to a temperature at which incipient retorting will takeplace. Thus the raw shale may be injected into a hot bed of inert andnon-adsorbent particles previously utilized, to preheat the raw shale bydirect heat exchange. The latter forms a feature of the invention.

The invention will be better understood by referring to the accompanyingdrawings in which Figure 1 shows diagrammatically a system or apparatusfor the retorting of a shale, using the heat of the burning spent shaleto indirectly heat the raw shale as it is introduced for processing.

Figure 2 shows a system and apparatus generally similar to that ofFigure l incorporating the additional feature of pressurizing andpreheating the raw shale and releasing it to a relatively lower pressurefor more complete disintegration.

Referring first to Figure 1, there is shown a reactor vessel 11 havingan upper zone 13 and a lower zone 15 separated by a transfer partitionelement 17. Fluidized solid materials are introduced into the upper zone13 and aerated with a suitable gasiform fluid such as steam orhydrocarbon gases so as to produce a dense turbulent mass having anupper interface 19 which tends to maintain a more or less regular levelunder stable operating conditions. After the retorting operation isunder way the retorting itself may supply substantially all of theaeration fluid required, except necessary bleeds or special jets whichmay be required for circulation, etc. Gas required for circulation inloops or dip legs may supply all aeration required, above that obtainedfrom retorting.

Coils or manifolds 21 preferably extend from the zone 13 into the lowerzone 15 so that solids can be circulated through them and be heatedindirectly by a mass in zone 15.to be described.

Fresh shale, suitably ground or pulverized, preferably to a size below 4inch, is introduced into zone 13, with suitable aeration or otherconveying means through a tube 25. Any suitable means for feeding theground or crushed shale may be used, such as a screw feeder, e. g. thatshown at'81 in Fig. 2. The bed 13 may be aerated by conventional means,indicated diagrammatically at 27, if required.

Bed 13 is composed of a substantial proportion of relatively large inertparticles having a minimum size of about 70 microns and preferably aminimum of about microns average diameter. A considerable mass of thisrelatively large particle inert and smooth surfaced material is used andfluidization should be suificiently active that there is substantialmovement within the bed so as to enhance the grinding or attrition ofthe shale particles introduced through line 25. The relatively large,smooth, inert particles should have a packed density of at least one andpreferably greater than one (density of Water: 1 Such density, measuredwhen the solids are unfluidized, also called the apparent density,enhances separation of the less dense spent shale particles and such abed is quite different from a conventional bed of spent shale residues.

The fluidizing velocity of the gases passing upwardly through bed 13must be great enough to obtain complete fluidization of the coarse inertparticles and preferably is as high as can be tolerated withoutexcessive elutriation of the raw shale before it is stripped of its oil.In general, the gas velocity should be at least two feet per second andin many cases it may be considerably higher up to feet per second ormore, depending on the density and granular size of the inert solids.

The hydrocarbon and other volatile gases or vapors carrying the spentshale residues are passed into a cyclone separator 31 of conventionaltype where entrained spent shale is separated and passed downwardthrough the tube 33. The hydrocarbons and other recovered organicproducts are taken through tube 35 upwardly for recovery and/ or furtherprocessing.

The spent shale residue passes down through tube 33. Part of it may bewithdrawn from the system, if desired, through a valve 37. Ordinarily,however, a larger part of it is diverted into a connecting tube 39controlled by valve 41. Tube 39 leads into the bottom zone where thespent shale is burned. Air or other oxidizing gas is introduced into thebottom of zone 15 through a tube 45 and preferably through a suitablegrid of conventional type 47. The air velocity should be such that thespent shale is fluidized, the upper level of the dense fluid bed thusformed substantially surrounding the manifold or coils 21 through whichthe particles in the retorting bed 13 are being circulated for heattransfer to the retorting zone 13. Spent shale, after burning, may bewithdrawn through a tube 49 controlled by valve 51 and/ or recoveredfrom the cyclone dip leg 59.

Other methods of heating the bed 15 may be used, such as burning wastegases from the process or other extraneous sources. Also, other indirectmethods of heating bed 13 may be used such as coils in bed 13 throughwhich retorted shale fines, etc., are circulated and burned with air oroxygen.

The uper level of the dense phase indicated at 53 is preferably well uparound the coils or loops 21 so that the heating coils and the solidstherein may be heated as eflicien-tly as possible. Suitable means suchas steam jets 54 are provided for causing a rapid circulation ofretorting bed solids, through the indirect heat exchanger means providedby coils or manifolds 21. The rapid circulation through coils 21 isrequired to provide heat of retorting for the retorting zone.

The flue gases from the spent shale are passed upwardly through a tube55 and through a conventional cyclone 57 from which solids are takendownwardly through pipe 59 for discharge or re-addition to heating zone15. The solids-free flue gases are taken out through stack 61 to theatmosphere or to other disposal means.

By utilizing the indirect heat exchangers 21 the retort may bemaintained at high temperature without contaminating the gases releasedtherefrom with the combustion gases in zone 15. The preheated shale israpidly pulverized in the turbulent bed 13 by the impact of the largeinert solid particles, steel shot, sea sand, small pebbles or the like,which pounds the shale rapidly into a very fine powder. As noted above,this fine powder separates readily from the smooth inert solids whichare relatively much larger and quite non-adsorbent. From this finepowder the recoverable oil and other organic gases and vapors mayrapidly be recovered to a maximum extent.

Referring now to Figure 2 there is disclosed a reaction vessel 71 which,in general, is quite similar to vessel 11 of Figure 1. It has an upperzone 73, with dense phase interface 74, a lower zone 75, with a densephase interface 76, a cyclone 77 and a transverse partition 78 which aresimilar, in general, to the corresponding elements of Figure 1. A dipleg or loop 79, or a plurality of such, is.

provided to convey mixed solids from bed 73 through lower bed 75 forheat transfer. Aerating gas to effect circulation through 79 is suppliedthrough an inlet 80.

Raw shale to be introduced into the system of Figure 2 is fed through apressurizing device 81, e. g. a screw type feeder, and suitablypressured with a hydrocarbon gas or with steam supplied through a line83. The raw shale then enters a manifold which has substantiallyimmersed in the fluidized spent shale bed 75 coils or other branches 87,provided to pass through the bed and extract heat therefrom. Steam orother aerating gas is supplied to the coils 87 through a suitable lineor manifold 88.

The fresh shale subjected to the preheating treatment and pressurizingjust described is permitted to expand rapidly through one or preferablyseveral expansion nozzles 89. Means such as nozzles or manifold 93 maybe provided for introducing additional aerating gas, if re quired. Suchaerating gas may be a hydrocarbon gas or steam, or it may be an inertgas if desired.

As in the case of Figure l the upper zone 73 contains a mass ofrelatively large, smooth, non-adsorbent and inert particles such assteel shot, small pebbles or sea sand which are actively fluidized underoperating conditions. The preheated shale, largely disintegrated uponexpansion or pressure release from nozzles 89, is further disintegratedby both the heat received from and the impact between the larger solidparticles in bed 73.

The hydrocarbon and other volatile gases pass upwardly into cycloneseparator 77 and to a recovery system (not shown) through tube 95. Thespent shale is separated in the cyclone and is conducted downwardly andout of the reactor through tube 97 to a discharge valve 99. Preferably amajor part, and in some cases all, of the shale is diverted into tube1&1 controlled by valve 103 from which it passes to the shale burningbed 75. As in the case of Figure l the shale is burned in bed 75 byintroducing air or other oxidizing gas through tube 105 and grid 107,the gas velocity being suflicient to keep the bed fluidized to a heightWell up around the preheating coils 87. The combustion gases with someentrained spent shale fines pass upwardly through tube 109 to cycloneseparator 111. From the latter the gases pass out through tube 113 to astack or other disposal device. The spent shale fines may be dischargedfrom the bottom of the cyclone through tube 115 and other spent shalemay be withdrawn from the reactor through tube 1117 controlled by valve119.

The particular combination of means for disintegrating the shale bymeans of successive pressurizing with gases and releasing, followed byattrition between large inert particles expedites the recovery of oilfrom shale and constitutes a major advantage of the invention. It willbe understood, of course, that the system can be varied somewhat and maybe applied to finely divided coal which is to be converted by expansionor otherwise. The system may also be applied to other materialsundergoing similar processing.

What is claimed is:

A process for distilling oil shale to recover oil vapors therefrom whichcomprises the steps of: passing subdivided raw shale through apreheating zone, introducing a gas under pressure into said preheatingzone, suddenly releasing preheated and pressurized shale into the upperportion of a retorting zone maintained at a reduced pressure andcontaining a fluidized mass of particulate inert solids above 70 micronsin size maintained at a distillation temperature, said inert solidsbeing relatively smooth, non-absorbent, and attrition resistant andhaving a packed density greater than 1, the proportion of shale in saidmass being less than 25%, said mass being fluidized at a gas velocityabove 2 ft./sec. sufiiciently high to entrain shale residue but at a gasvelocity below the entrainment velocity of said inert solids, wherebyvolatile constituents are distilled from said shale and said shale isreduced to a more finely divided shale residue, removing overhead saidvolatile constituents and said finely divided shale residue, separatingin a cyclone separating zone said shale residue from said volatileconstituents, transferring the shale residue so separated to a burningzone below said retorting zone, fluidizing and burning said shaleresidue in said burning zone with an oxidizing gas at a temperaturesubstantially higher than said distillation temperature, circulatingportions of said mass through indirect heat exchange with the burningspent residue whereby said mass is maintained at said distillationtemperature, and removing flue gases and burned shale residue from saidburning zone.

References Cited in the file of this patent UNITED STATES PATENTSJohnson May 2, 1944 Krebs Nov. 28, 1944 Yellott July 18, 1950 KearbySept. 18, 1951 Ogorzaly Nov. 25, 1952 Krebs Feb. 3, 1953 Carr June 23,1953 Nicolai Dec. 21, 1954 FOREIGN PATENTS Great Britain Dec. 1, 1922

